Install pixi,
then for each new project, create a new empty pixi environment
pixi my_new_project
Then get into the newly created directory my_new_project
cd my_new_project
and install what you need
from conda-forge, for example
pixi install python
then if you also need packages from PyPi, like pyxel, install them with
pixi install --pypi pyxel
Develop your project with your favorite editor, for example Visual Studio Code,
and when you need to run your code, just type
pixi run python my_app.py